SOD1 and asthma: Serum SOD activity was lower in ETS-exposed asthmatic subjects than in non-exposed asthmatic subjects (SOD U/ml serum: non-ETS asthma (n = 342), 18.2±0.6; ETS asthma (n = 136), 14.7±0.9;p = 0.04) (FIGURE 1).